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Issue Information

  •  23 November 2021
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Ocean Surface Radial Velocity Imaging in the AT‐INSAR Velocity Bunching Model: A Functional Approach

  •  5 November 2021

Key Points

  • The scalar field of radial velocities of a simulated ocean surface is constructed from a noisy along-track interferometric synthetic aperture radar (AT-INSAR) image of that surface

  • The nonlinear integral equation that relates radial velocities to AT-INSAR intensities is solved by Newton's methods on function spaces

  • Robustness is illustrated by recovering fields of radial velocities for different R/V ratios and other radar parameters

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Issue Information

  •  27 October 2021
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Calibration of the JUICE RWI Antennas by Numerical Simulation

  •  25 October 2021

Key Points

  • The antennas of the Radio Wave Instrument (RWI) onboard Jupiter Icy Moons Explorer were calibrated by numerical computer simulations

  • Results include the calculation of effective lengths vectors, antenna impedances, and high-frequency characteristics

  • Strong active radar pulses should not harm the RWI and Langmuir probe receivers

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Bandwidth‐Enhanced Ultra‐Wide Band Wearable Textile Antenna for Various WBAN and Internet of Things (IoT) Applications

  •  24 October 2021

Key Points

  • Compact asymmetric CPW fed monopole antenna using denim fabric as substrate applicable for UWB communication

  • The final antenna produces a peak gain of about 6.57 dBi and achieved omnidirectional radiation patterns

  • On-body measurements and deformation through bending is performed to provide validation to the structure

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Estimation of the Mode Conversion Effect on the Determination of Southern Boundary for the ∼100 MeV Electron Precipitations

  •  7 October 2021

Key Points

  • The influence of the ultraenergetic relativistic electron precipitations on mode conversion in the terrestrial waveguide was analyzed

  • New statement of a mode conversion problem was used

  • The effect of a normal wave conversion may be neglected in the problem of southern boundary determination if the precipitations are not powerful

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A Comparison of the Topside Electron Density Measured by the Swarm Satellites and Incoherent Scatter Radars Over Resolute Bay, Canada

  •  7 October 2021

Key Points

  • Swarm-measured electron densities are smaller than those measured by incoherent scatter radars (ISR) radars at conjunctions by about 35%

  • The linear fit line to Swarm vs. ISR electron density plots has a slope of ∼0.62

  • The effect of smaller Swarm electron densities is stronger at nighttime

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Issue Information

  •  27 September 2021
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A Modeling Framework for Estimating Ionospheric HF Absorption Produced by Solar Flares

  •  23 September 2021

Key Points

  • A new high frequency (HF) absorption model reproduces observations more accurately than the existing D-region Absorption Prediction model with an average skill score of 40%

  • Incorporating a broad range of solar irradiance wavebands and plasma-neutral interactions can significantly improve HF absorption prediction

  • Model results suggest changes in the D-region electron temperature can impact the HF absorption experienced by traveling radio waves

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Using the World Wide Lightning Location Network (WWLLN) to study Very Low Frequency transmission in the Earth‐Ionosphere Waveguide: 2. Model test by patterns of detection/non‐detection

  •  2 December 2021

Key Points

  • Suppression of low-latitude VLF transmission propagating magnetic West, especially in night

  • New finding: The magnetic-westward suppression at night applies to nearly the entire westward half-plane, from magnetic-South clockwise to magnetic-North

  • New finding: The magnetic-westward suppression at night is readily observable for dip angles in the range -30° to +30°

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Multiyear detection, classification and hypothesis of ionospheric layer causing GNSS scintillation

  •  4 November 2021

Key Points

  • A survey of half a solar cycle of auroral GNSS scintillation data is conducted

  • Scintillation occurrence rate decreases with the waning solar cycle

  • For phase events, the hypothesized irregularity layer altitude decreases with the waning solar cycle

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The Distribution Characteristics of GPS Cycle Slip Over the China Mainland and Adjacent Region During the Declining Solar Activity (2015–2018) Period of Solar Cycle 24

  •  23 April 2021

Key Points

  • The temporal and spatial characteristics of cycle slips are analyzed using the GPS data detected from almost 260 observations in the China sector during the period of the year 2015–2018

  • The variations of cycle slip are dependent on the local time, seasons, solar activity, and latitudes

  • The feature of cycle slip occurrence is related to the solar activity and distribution of ionospheric scintillation above a certain intensity level over the China region

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Global Positioning System Observations of Ionospheric Total Electron Content Variations During the 15th January 2010 and 21st June 2020 Solar Eclipse

  •  23 April 2021

Key Points

  • Solar eclipse is a phenomenon that has a direct influence on the Earth's ionosphere

  • The measure of the decrease in vertical value of total electron content during the eclipse hours are correlated with the partial and complete obscuration of solar radiation

  • The scale of the reduction is closely associated with the eclipse magnitude

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High‐Precision Carrier Tracking Algorithm for Extremely Weak and High‐Dynamic Signals

  •  23 April 2021

Key Points

  • A novel low pass denoising method is proposed

  • A improved PLL with excellent performance is achieved

  • The proposed method is suitable for high-precision carrier tracking in deep space exploration, especially for high-dynamic and weak signals

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Superconducting Receiver Technologies Supporting ALMA and Future Prospects

  •  18 April 2021

Key Points

  • We developed highly sensitive terahertz receivers for the Atacama Large Millimeter/submillimeter Array

  • Seventy-three receivers with NbTiN-based superconducting mixers were successfully produced at the National Astronomical Observatory of Japan

  • Next-generation receivers to enhance the capabilities of the current telescope are being developed

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A Detection Performance Analysis of Sanya Incoherent Scatter Radar Tristatic System

  •  16 April 2021

Key Points

  • Multistatic phased array Incoherent scatter radars (ISR) equation for soft target is derived

  • The detection performances of phased array monostatic and bistatic ISR are analyzed for pulse width, height, beam width and scattering volume

  • Optimal tilt and rotation angles of receiving array are suggested for Sanya incoherent scatter radar (SYISR) tristatic system

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Data Assimilation Retrieval of Electron Density Profiles From Ionosonde Virtual Height Data

  •  16 April 2021

Key Points

  • New method to retrieve the bottom side electron density from virtual height data is developed based on Kalman filter equations

  • The derivation of the Jacobian for virtual height data assimilation is presented

  • The assimilative inversion of virtual height data outperforms the polynomial analysis inversion algorithm

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Holographic Calibration of Phased Array Telescopes

  •  15 April 2021

Key Points

  • Holographic aperture imaging for phased array telescopes is presented

  • Suggested technique requires few resources and can be used for calibration

  • Technique was successfully tested on prototype station of SKA-Low

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Calibrating the Amplitude and Phase Imbalances in AgileDARN HF Radar

  •  14 April 2021

Key Points

  • Developed a calibration mode and proposed a complete system calibration method for Agile Dual Auroral Radar Network radar

  • Inject two signals to eliminate the errors among transceivers, enabling the amplitude and phase mismatches to reduce to 0.2 dB and 1°

  • Employ the linear least squares fitting with meteor echoes for antenna calibration, facilitating the array pattern close to an ideal one

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Statistics of total electron content depletions observed over the South American continent for the year 2008

Key Points

  • First time regional plots of TEC depletions
  • New numerical algorithm developed to automatically detect TEC depletions
  • Day-to-day variability of TEC depletions in a regional basis

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Relative detection efficiency of the World Wide Lightning Location Network

Key Points

  • A relative detection efficiency model for the WWLLN is developed
  • The model is used to analyze current and past network performance
  • The performance effects of a single station outage are examined

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An Indoor Path Loss Prediction Model Using Wall Correction Factors for Wireless Local Area Network and 5G Indoor Networks

Key Points

  • A modified effective wall loss model (EWLM) for indoor environment is presented
  • Real-time measurements and simulations for various indoor path loss models are used
  • Several frequency spectrum band were considered for evaluation purposes

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Measurement of Ionospheric Total Electron Content Using Single‐Frequency Geostationary Satellite Observations

Key Points

  • The derivation of total electron content using single-frequency terrestrial GPS receivers and geostationary satellites is demonstrated
  • The demonstrated technique is validated by correlation analysis
  • The correlations between TEC time series for pairs of receivers and between receivers and an ionosonde over a year show good agreement

Plain Language Summary

The ionized upper portion of the atmosphere is known as the ionosphere. The ionosphere interferes with signals traveling between satellites and the ground and can cause errors in satellite navigation, surveillance, and communication systems. The impact of these errors can be reduced if we are able to measure the total electron content (TEC), which can be simply thought of as the total number of electrons in a straight line between a satellite and the ground. We have developed a technique that allows us to measure TEC using receivers measuring single-frequency signals from geostationary satellites. This is useful because it will increase the number of measurements available and because using geostationary satellites makes the measurements relatively easy to interpret. To test the technique we use a correlation analysis to compare measurements made by the single-frequency receivers. We also correlate technique measurements with independent TEC observations made by an ionosonde. All correlation results showed good agreement, suggesting consistency for the technique, and that the technique is reliable. The demonstrated technique has the potential to become a routine method to derive TEC, which will help to map the ionosphere in real time.

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Accurate measurements of the dielectric constant of seawater at L band

Key Points

  • Dielectric measurements of seawater are made with a microwave cavity at 1.413 GHz
  • Measurements are made as a function of temperature and salinity for values found in open ocean
  • Accuracy is better than 0.3 for both real and imaginary parts of the dielectric constant

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Software‐Defined Radio Decoding of DCF77: Time and Frequency Dissemination with a Sound Card

Key Points

  • DCF77 signals are used for time of flight measurement using Software-defined radio processing
  • A 10 μs resolution time measurement and sub-ppm frequency resolution with a sound card are demonstrated
  • Ionospheric delay characterization for educational purposes and long-term instigation with low-cost equipment has been developed

Plain Language Summary

Software-defined radio aims at reducing to its minimum the hardware setup needed to process radio frequency signals and relies on software processing for demodulation: here we demonstrate the precise measurement of an atomic clock-locked emitter, propagating at very low frequency, using only a general purpose computer sound card. Thanks to the high accuracy of the time of flight accessible through an improved modulation schemes, such physical properties as ionosphere altitude and ground wave versus air wave are detected. The frequency of the atomic clock is compared with the sound card local oscillator frequency, demonstrating the temperature dependence of the latter, readily measured in this experiment.

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Calculating the absorption of HF radio waves in the ionosphere

Key Points

  • Either the Appleton-Hartree or Sen Wyller dispersion relation can be used to calculate absorption
  • It is necessary to utilize the correct collision frequency specification for each dispersion relation
  • Geophysical variations of collision frequency should be included in absorption calculations

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Fresnel Reflection and Transmission Coefficients for Temporally Dispersive Attenuative Media

Key Points

  • General expressions for Fresnel reflection and transmission coefficients for homogeneous and inhomogeneous plane waves are derived for TE- and TM polarized plane waves in complex media with loss
  • The critical angle for total internal reflection remains unchanged when material loss is included; the polarizing angle (for a TM polarized plane wave is changed otherwise, a pseudo Brewster's angle occurs at which the magnitude of the TM) polarization reflection coefficient is a minimum
  • Total reflection at grazing incidence on the optically denser medium does not occur when both media exhibit loss; total reflection does not occur at critical incidence when both media exhibit loss.

Plain Language Summary

Amplitude reflection and transmission coefficients for a time-harmonic electromagnetic plane wave incident upon a plane interface separating two different lossy media are developed.

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Digital transmission techniques for a long haul HF link: DSSS versus OFDM

Key Points

  • Advanced modulation techniques applied to HF communications
  • Spread spectrum and OFDM modulations for ionospheric transmissions

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